diff --git a/src/r_defs.h b/src/r_defs.h
index bebe16fd6b..c69450e01d 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -431,7 +431,7 @@ public:
 	}
 
 	bool CopyPlaneIfValid (secplane_t *dest, const secplane_t *opp) const;
-	inline double secplane_t::ZatPoint(const AActor *ac) const;
+	inline double ZatPoint(const AActor *ac) const;
 
 };